About This Item
Used Mikawa Shiro Nagura Koma 1lb. 3.8oz. (560.4g) Japanese Natural Sharpening Stone
It has Koma nagura hand writing on the sharpening surface by former owner. I am not original buyer from the mine. Someone former owner made beautiful work wooden block.
It raises great amount of dark gray or light black color slurry. It is very smooth stone, and it does not need tomo nagura or the device to produce the slurry (worn Diamond lapping stone).
(Scale; 1 to 10, 1-3 is very soft muddy rough grit whetstone 3-6 is soft medium grit whetstone, 6-8 is hard medium grit whetstone; 8-10 is fine grit whetstone)
It makes my blue II steel kasumi blade knife Hagane became bright silver color finish with tiny lines of scratches. Jigae became vivid frosted silver color finish.
(Scale; 1 to 10, 1-3 give deep scratch marks to the steel, 3-5 is delete the 1-3 scratches, 5-8 makes the steel cloudy, 8-10 makes the steel semi-mirror finish or mirror finish)
According to Dr. Kuniichi Tawara who is a Metallurgy doctor, and very famous Japanese sword researcher, Koma molecule is 10 to 20 micron. It is used right before sharpening Uchigumori whetstone in Japanese sword sharpening to delete whetstone marks from one before process, Chu Nagura sharpening. It should be right before or beginning of fine grit sharpening. For razor sharpening, it is used one before the process sharpening by fine grit whetstone like Nakayama, Ozuku, Wakasa, etc.
I t is for sharpening Japanese sword or razor blade or high carbon steel Koma has used by Japanese sword sharpening masters and the other craftsmen for a long time, so it has run out the mine at first. That is why it is dealing with higher price like double of the amount or triple of the amount comparing with the other Nagura layers stones. Koma is one of the twelve layers of the Mikawa shiro nagura mine. It is hardest to find among Mejiro, Tenjo, Botan, Koma, Ban, and Atsu, etc. Those nagura names derive from layer in Shiro Nagura mine. Koma is not only the finest Shiro Nagura in the layers, but it has also strong whet power.